The long-term objectives of this work are to elucidate the molecular basis of pattern formation during development in Drosophila melanogaster. The characterization of a genetic component of the Wingless signaling pathway in the Drosophila embryonic epidermis will serve to define elements required for regulation of developmental decisions in invertebrates and, by analogy, vertebrates. The molecular cloning of arrow, a newly identified member of the Wingless pathway, will be performed and will facilitate subsequent studies designed to further identify the role arrow plays in the Wingless pathway. The generation of antibodies specific to the Arrow protein will aid in determining its cellular localization. Genetic epistasis and embryonic microinjection will provide information regarding the location, and possibly the mechanism of action, of arrow in the Wingless pathway. The implications of this work lie in the possibility that this genetic cascade will provide insights into mechanisms of vertebrate development as the Wingless pathway utilizes a novel form of signal transduction and is highly conserved evolutionarily.